diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2018-04-05 16:25:12 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-04-05 21:36:27 -0700 |
| commit | 3eda69c92d4751977baf2d34e88a29d4b6affa7d (patch) | |
| tree | 931b5551d4d8a4732375d10f2babac7d74628798 | |
| parent | 0c7c1bed7e13dbb545375c231e6ba1dca5e8d725 (diff) | |
kernel/fork.c: detect early free of a live mm
KASAN splats indicate that in some cases we free a live mm, then
continue to access it, with potentially disastrous results. This is
likely due to a mismatched mmdrop() somewhere in the kernel, but so far
the culprit remains elusive.
Let's have __mmdrop() verify that the mm isn't live for the current
task, similar to the existing check for init_mm. This way, we can catch
this class of issue earlier, and without requiring KASAN.
Currently, idle_task_exit() leaves active_mm stale after it switches to
init_mm. This isn't harmful, but will trigger the new assertions, so we
must adjust idle_task_exit() to update active_mm.
Link: http://lkml.kernel.org/r/20180312140103.19235-1-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | kernel/fork.c | 2 | ||||
| -rw-r--r-- | kernel/sched/core.c | 1 |
2 files changed, 3 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index f71b67dc156d..242c8c93d285 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -595,6 +595,8 @@ static void check_mm(struct mm_struct *mm) void __mmdrop(struct mm_struct *mm) { BUG_ON(mm == &init_mm); + WARN_ON_ONCE(mm == current->mm); + WARN_ON_ONCE(mm == current->active_mm); mm_free_pgd(mm); destroy_context(mm); hmm_mm_destroy(mm); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 28b68995a417..e8afd6086f23 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5560,6 +5560,7 @@ void idle_task_exit(void) if (mm != &init_mm) { switch_mm(mm, &init_mm, current); + current->active_mm = &init_mm; finish_arch_post_lock_switch(); } mmdrop(mm); |